1. Field of the Invention
This invention relates to a heat dispersion device for use with an electronic apparatus, and more particularly to a novel heat dispersion device provided with an air duct.
2. Description of the Prior Art
At least one power transistor or an integrated circuit containing a number of semiconductive elements may be used in an electronic apparatus for the amplification of an audio signal or a video signal. Such power amplifying electronic elements generate much heat because they consume large amounts of power as compared with other parts, for example, a stage for amplifying an intermediate frequency signal. As is generally known, semiconductive elements are sensitive to heat and are susceptible to break-down when too much heat is generated by the semiconductive elements. Therefore, power amplifying electronic elements are usually mounted on a heat dispersion device referred to as a "heat sink", whereby the heat generated by the electronic element or elements is transmitted to the heat dispersion device and from the latter to the atmosphere for minimizing the temperature-rise of the electronic element or elements.
An existing type of heat sink is formed of aluminum and has a number of heat-dispersing fins. The heat sink is colored black and the power amplifying electronic element is mounted in a hollow or recess formed by a number of the heat-dispersing fins. Heat generated by the electronic element is dispersed only by the radiation thereof to the atmosphere from the heat-dispersing fins, or the heat is transmitted to the chassis on which the heat sink is mounted. In order to obtain a sufficient heat-dispersing effect merely by radiation from the heat-dispersing fins, it has been necessary to employ a heat sink of large dimensions for providing a large heat-dispersing surface. However, by increasing the size of the heat sink, a satisfactory heat-dispersing effect cannot always be obtained, but there is the further disadvantage that the cost of the heat sink is increased with its size. Since there is the possibilty that the temperature in a casing or cabinet containing the heat sink may rise appreciably because of the poor heat-dispersing effect, the heat sink is often mounted on the outside of the casing. However, in this case, there is the danger that the user may touch the heat sink and suffer burns therefrom. Further, with the existing type of heat sink having heat dispersing fins, the number and dimensions of the fins have to be designed for the specific heat-generating electronic element or elements to be mounted thereon, for example, a heat sink for use with a single power transistor, as in a monaural audio system cannot be used, or readily adapted for use with the plural power transistors required in a stereophonic system.
Another type of conventional heat dispersion device in use consists of an air duct of metal mounted directly on the power transistor. The air duct works to disperse the heat generated by the power transistor and to lead the heated air upwardly therefrom. This type of heat dispersion device is effective for a single power transistor of small capacity, but it is not suitable for the dispersion of heat from a plurality of the power transistors or from a power transistor of large capacity.